1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device wherein minutely isolated resist patterns are formed and the side walls thereof are roughened. More concretely, the present invention relates to a method of forming minutely isolated resist patterns in which a space between patterns and the size of a hole are reduced. The present invention further relates to a method of roughening the side walls of the minutely isolated resist patterns after etching.
2. Background Art
The width of an interconnection runner and the space between interconnection runners required to manufacture a semiconductor device are greatly reduced as the degree of integration of a semiconductor device is increased. Minute patterns are usually formed by forming a resist pattern through use of photolithography and by etching various thin films beneath the resist pattern while using the resist pattern as a mask.
For this reason, photolithography becomes very important in forming a minute pattern. Photolithography comprises a resist coating process, a mask alignment process, an exposure process, and a development process. There is a restriction on the wavelength of light used for exposure, imposing a limitation on miniaturization of the pattern.
Methods described in Japanese Patent Application Laid-open Nos. 6-250379 and 7-134422 have already been proposed as methods of forming minute resist patterns smaller than the limit of wavelength of light for exposure purposes used by the existing photolithography. The methods utilize counter diffusion of resin components contained in first and second resists. Under these methods, the second resist is made of a material which is soluble in an organic solvent capable of dissolving the first resist, resulting in the first resist patterns being deformed.
Under a method used for removing the second resist, the second resist is removed and dissolved through use of a developer capable of generating an acid and dissolving the second resist upon exposure to light [e.g., TMAH (tetra-methyl-ammonium hydroxide)]. When the second resist is exposed to light, the first resist patterns beneath the second resist are also exposed to light and sometimes becomes solubilized. The thus-solubilized first resist patterns can be dissolved in a solution capable of dissolving the second resist. Therefore, there is a high risk of the first resist patterns being dissolved at the time of dissolving and removing the second resist, resulting in a small margin of error in the manufacturing process.
In a case where polyvinyl alcohol disclosed in Japanese Patent Application Laid-open No. 6-250379 is used as a second resist, several problems arise such as a small effect of the second resist or the poor topography of resist patterns produced after treatment. Further, since the second resist is developed through use of only water, the resist is not sufficiently rinsed, thus resulting in development residues, such as specks, being apt to arise in the pattern. Such development residues will cause defects to appear in resist patterns during a subsequent etching process.
As mentioned previously, it has been very difficult to form minute resist patterns smaller than the limit of wavelength of light for exposure purposes used for the existing photolithography, using the existing photolithography.
Although another technique has also been proposed which enables formation of resist patterns smaller than the limit of wavelength of light for exposure purposes, the technique suffers several problems, and hence it is difficult to apply the technique to actual manufacture of a semiconductor device.